Characteristics of Fluid Inclusions and Mineralization Indications of the Yechangping Mo Deposit,East Qinling
The Yechangping molybdenum(Mo)deposit is located in the middle East Qinling molybdenum oro-genic belt.Its metallogenic type mainly belongs to the skarn type in the early stage,followed by the porphyry type.In the East Qinling molybdenum mineralization belt,there are relatively fewer studies focusing on the fluid inclusions of the skarn-porphyry composite molybdenum deposits,particularly their fluid evolution charac-teristics and the metallogenetic mechanisms,which are essential to understanding ore genesis.This study clas-sifies the hydrothermal mineralization stages of the Yechangping Mo deposit from early to late as follows:early silica and late silica quartz-potassic stage(stage Ⅰ:quartz),quartz-pyroxene stage(stage Ⅱ:quartz,main mineralization stage),quartz-polymetallic sulfide stage(stage Ⅲ:quartz),and quartz-carbonate stage(stageⅣ:quartz).Based on this preliminary study,inclusion samples were collected from stages Ⅰ to Ⅳ quartz and analyzed using microscopy,micro-thermometry,and laser Raman microprobe.The results show that the types of fluid inclusions within the quartz are NaCl-H2O gas-rich type(WG type),NaCl-H2O liquid-rich type(WL type),CO2 type(C type),and daughter mineral-bearing type(S type).From the early to the late stage of mineralization,the homogeneous temperatures of fluid inclusions are concentrated at 380-437 ℃,331-370 ℃,312-320 ℃ and 257-350 ℃,corresponding to average salinity(NaCleqv)of 10.83％,9.29％,7.16％,and 4.51％,respectively.The mineralizing fluids gradually evolved from a high-temperature,medi-um-high salinity,and CO2-rich NaCl-H2O-CO2 system at the early stage to a low-temperature,low-salinity,and CO2-poor NaCl-H2O system at the late stage.The fluid mixing effect leads to a decrease in fluid tempera-ture and salinity,and the fluid transforms from an oxidized state to a reduced state.This results in a drastic decrease in the solubility of the Mo element in the fluid,and the rapid unloading and precipitation of Mo.Con-sequently,we constructed a mineralization model on the scale of mining area based on the"magma-fluid-con-struction"mineralization system.
East Qinling molybdenum ore beltYechangping molybdenum depositsilica-porphyry molybde-num depositfluid inclusion
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